Solid elastomeric block copolymers

ABSTRACT

There are disclosed novel, solid, elastomeric block copolymers with improved resistance to cold flow wherein either 1) the terminal blocks are each a polymer (I polymer) of at least one conjugated diene I, e.g., isoprene, which contains at least five carbon atoms with at least one of each pair of double-bonded carbon atoms in the polymerized diene I units being additionally single-bonded to two carbon atoms; at least one middle or interior block is a hydrogenated polybutadiene (B polymer); and at least one middle or interior block is an essentially straight chain polyethylene (E polymer) resulting from the hydrogenation of a polybutadiene composed of at least 80% of 1,4- units; or 2) the terminal blocks are random IB copolymers of at least one diene I as previously defined and hydrogenated butadiene, and at least one middle or interior block is a straight chain polyethylene (E polymer) as previously defined. The hydrogenated butadiene units in the B polymer or random IB polymer blocks are composed of no more than about 65% of 1,4- units and at least about 35% of 1,2- units. 
     The foregoing block copolymers may be prepared by selectively hydrogenating substantially all the butadiene units of a precursor block copolymer wherein the precursor blocks of the straight chain polyethylene blocks units are polybutadiene blocks in which at least about 80% of the butadiene units are 1,4- units. A sufficient number of I units in the I polymer blocks or random IB copolymer blocks retain their unsaturation on selective hydrogenation to enable the vulcanization of the block copolymer

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of application Ser. No. 08/143,718, filedNov. 1, 1993, now U.S. Pat. No. 5,352,743, which is a division ofapplication Ser. No. 07/836,577, filed Feb. 18, 1992, now U.S. Pat. No.5,276,100, which is a continuation-in-part of applications Ser. Nos.07/466,233, filed Jan. 16, 1990, now U.S. Pat. No. 5,187,236, and07/735,552, filed Jul. 25, 1991, now U.S. Pat. No. 5,292,820.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to novel, solid, elastomeric block copolymershaving a degree of unsaturation sufficient for desired vulcanization orcross-linking, or other chemical modification, but not so high as tocause the copolymer to be susceptible to an undesirably large amount ofoxidative, thermal or photolytic degradation, and also having improvedresistance to cold flow and improved "green" strength beforevulcanization.

2. Information Disclosure Statement Including Description of Related Art

The following information is disclosed in accordance with therequirements of 37 CFR 1.56, 1.97 and 1.98.

Elastomers (or rubbers) of either natural or synthetic origin usuallyrequire vulcanization for transformation into insoluble, non-deformablehigh strength elastomeric products. Before vulcanization, rubberspossess inferior properties and low strength which limit their utility.

There are a number of well known methods for achieving thevulcanization, also referred to as cross-linking, of unsaturatedelastomers. Such methods include the use of sulfur and accelerators,peroxides, benzoquinone dioxime, certain phenolic resins and similaragents. Any of the above or any other well known vulcanizing techniquesmay be utilized to cross-link the elastomers of this invention.

The great majority of currently known synthetic elastomers are based onpolymers or copolymers of butadiene or isoprene. These polymers, whichinclude cis-polybutadiene, emulsion polybutadiene (EBR),styrene-butadiene copolymer (SBR), butadiene-acrylonitrile copolymer(NBR) and cis-polyisoprene, provide raw materials for the production ofa very large volume of rubber goods, such as automotive tires, conveyorbelts, adhesives, footwear, sponge and mechanical goods. Because of thehigh degree of unsaturation inherent in the polymeric backbones, theseelastomers are easily and quickly vulcanizable alone or in blends. Asecondary consequence of the high degree of backbone unsaturation is theinstability of such elastomers in the presence of ozone and oxygen, bothof which promote rapid deterioration of these elastomers.

Butyl rubber, which is a copolymer of isobutylene and 2-3% by weight(wt.) of isoprene, represents a class of elastomers far more resistantto oxygen and ozone than those based on butadiene or isoprene. Thebackbone of butyl rubber is primarily polyisobutylene (which provides asaturated spine) into which there is randomly copolymerized about 2-3%by wt. isoprene to provide unsaturated sites for vulcanization. Butylrubber finds limited use because of its relatively poor elastomericproperties, and is used primarily in applications which take advantageof its damping properties, weathering resistance and low gaspermeability.

Ethylene-propylene-diene rubber (EPDM) has enjoyed substantialcommercial growth as a synthetic rubber since it combines excellentoxidation resistance with good elastomeric properties. This elastomer isprepared by the polymerization of ethylene, propylene and anon-conjugated diene, such as 1,4-hexadiene, dicyclopentadiene orethylidene norbornene. Diene incorporation is typically 5-10% by weight(wt.). The diene is randomly incorporated into the saturatedethylene-propylene backbone to provide pendant vulcanization sites.

The above prior art elastomers, with either high or low levels ofunsaturation, are characterized in that, having random unsaturation,they are randomly cross-linked all along the molecular backbone duringvulcanization. The success of vulcanization in incorporating allmolecular chains into the final cross-linked network with minimal "looseends" is termed the degree of network perfection. In order to insure thehighest degree of network perfection attainable, randomly unsaturatedelastomers must be cross-linked extensively. The large number ofcross-links necessary (12 to 40 per 100,000 molecular weight) dictatesthat the average distance between cross-links (M_(c)) must be relativelysmall in comparison with the dimensions of the whole molecule.Elastomeric properties, such as elongation, depend greatly on M_(c),e.g., the smaller the M_(c), the lower the elongation of the vulcanizedpolymer.

Highly unsaturated elastomers such as polybutadiene or natural rubberretain essentially all of their original unsaturation aftervulcanization. Such high level of backbone unsaturation causes theseelastomers to be very susceptible to degradation by oxygen, ozone, heatand light. Such inherent instability frequently necessitates the use ofappreciable amounts of expensive stabilizing additives and automaticallyrestricts the use of these polymers in areas where degradativeconditions are severe.

Another disadvantage of many prior art elastomers is that there isnothing in their molecular structure before vulcanization to preventtheir deformation when subjected to external forces. This manifestsitself as a lack of "green" strength and a low resistance to cold flowcaused by gravity or other forces to which the polymer is exposed beforevulcanization, e.g., during shipment or storage.

Various block copolymers having excellent elastomeric properties,especially elongation, have been made in the past. For example, a blockcopolymer commonly known as KRATON, manufactured by Shell ChemicalCompany, which has outstanding properties at room temperature, is athermoplastic elastomer consisting of block segments of polymerizedstyrene units and polymerized aliphatic diolefin units, such asbutadiene or isoprene. The most common structure of KRATON is the linearA-B-A block, such as styrene-butadiene-styrene (S-B-S) orstyrene-isoprene-styrene (S-I-S). One of such rubbers is believed to bedescribed by Jones, U.S. Pat. No. 3,431,323. Jones discloses blockcopolymers containing block segments of polymerized vinyl arene monomerunits, e.g., styreno, butadiene monomer units, and vinyl arene units.After the block copolymer is prepared, it may be subjected tohydrogenation to such a degree that the unsaturation of thepolybutadiene block is reduced to less than 10% of its original value,while 10-25% of the poly-vinyl arene block segments are hydrogenated.Although the KRATON triblock copolymers have excellent elastomericproperties at room temperature, since they are thermoplastic materialsthey lose these properties at temperatures of about 80° C. (and higher).In addition, since these polymers are not chemically cross-linked, theyare soluble in many organic solvents. These latter two deficienciesplace some restrictions on the viable areas of application for thesepolymers.

Falk, JOURNAL OF POLYMER SCIENCE: PART A-1, Volume 9, 2617-2623 (1971),the entire contents of which are incorporated herein by reference,discloses a method of selectively hydrogenating 1,4-polybutadiene unitsin the presence of 1,4-polyisoprene units. More particularly, Falkdiscloses selective hydrogenation of the 1,4-polybutadiene block segmentin the block copolymer of 1,4-polybutadiene -1,4-polyisoprene -1,4-polybutadiene and in random copolymers of butadiene and isoprene,with both polymerizod monomers having a predominately1,4-microstructure. Selective hydrogenation is conducted in the presenceof hydrogen and a catalyst made by the reaction of organoaluminum orlithium compounds with transition metal salts of 2-ethylhexanoic acid.

Falk, DIE ANGEWANDTE CHEMIE 21 (1972) 17-23 (No. 286), the entirecontents of which are also incorporated herein by reference, disclosesthe selective hydrogenation of 1,4-polybutadiene segments in a blockcopolymer of 1,4-polybutadiene-1,4-polyisoprene-1,4-polybutadiene and arandom copolymer of 1,4-butadiene and 1,4-isoprene.

Hoxmeier, Published European Patent Application 88202449.0, filed onNov. 2, 1988, Publication Number 0 315 280, published on May 10, 1989,discloses a method of selectively hydrogenating a polymer made from atleast two different conjugated diolefins. One of the two diolefins ismore substituted in the 2,3 and/or 4 carbon atoms than the other.diolefin and produces tri- or tetra-substituted double bonds afterpolymerization. The selective hydrogenation is conducted under suchconditions as to hydrogenate the ethylenic unsaturation incorporatedinto the polymer from the lesser substituted conjugated diolefin, whileleaving unsaturated at least a portion of the tri- or tetra- ethylenicunsaturation incorporated into the polymer by the more substitutedconjugated diolefin.

Mohajer et al., Hydrogenated linear block copolymers of butadiene andisoprene: effects of variation of composition and sequence architectureon properties, POLYMER 1982, Vol. 23, September, 1523-1535, discloseessentially completely hydrogenated butadiene-isoprene-butadiene (HBIB),HIBI and HBI block copolymers in which butadiene has predominantly1,4-microstructure.

Kuraray K K, Japanese published patent application Number JP-328729,filed on Dec. 12, 1987, published on Jul. 4, 1989, discloses a resincomposition comprising 70-99% wt. of a polyolefin (preferablypolyethylene or Polypropylene) and 1-30% wt. of a copolymer obtained byhydrogenation of at least 50% of the unsaturated bonds of anisoprene/butadiene copolymer.

SUMMARY OF THE INVENTION

In accordance with this invention, novel, solid, elastomeric blockcopolymers with improved resistance to cold flow before vulcanizationare provided wherein either 1) the terminal blocks are each a polymer,denoted as "I polymer", of at least one conjugated diene I, e.g.,isoprene, which contains at least five carbon atoms with at least one ofeach pair of double-bonded carbon atoms in the diene I units inpolymerized form being additionally single-bonded to two carbon atoms;at least one middle or interior block is a substantially hydrogenatedpolybutadiene, denoted as "B polymer", comprising 1,2- and 1,4- units ashereinafter defined; and at least one middle or interior block is anessentially straight polyethylene denoted as "E polymer", and resultingfrom the hydrogenation of a polybutadiene block comprising at least 80%of 1,4- units. The foregoing block copolymer contains, for example, anaverage of about 1 to 50 wt.% of I polymer blocks, about 50 to 98 wt.%of hydrogenated butadiene (B) polymer blocks, and about 1 to 30 wt. % ofE polymer blocks, all based on the total weight of said block copolymer;or 2) the terminal blocks are each a random IB copolymer of at least onediene I and hydrogenated butadiene (B), both as previously defined, andat least one middle or interior block is an E polymer, as previouslydefined, such block copolymer comprising, for example, an average ofabout 70 to 99 wt. % of random IB copolymer blocks, and about 1 to 30wt. % of E polymer blocks, all based on the total weight of blockcopolymer, with the i units being an average of about 1 to 50 wt. % ofeach random IB copolymer block and the remainder being B units. Thestructure of the B or IB polymer blocks in both of the foregoing classesof block polymers contains sufficient branching such that afterhydrogenation, these blocks contain no more than about 10% ofpolyethylene crystallinity. This result is accomplished by introducingside branches into the butadiene or IB copolymer blocks, e.g., bycontrolling the microstructure of polymerized 1,3-butadiene. Moreparticularly, the side branches are introduced into the polymer byinsuring that the polymerized butadiene contains a sufficient amount of1,2- units to prevent the selectively hydrogenated polymer from beingexcessively crystalline. Thus, the polymerized butadiene in the Bpolymer or IB copolymer blocks must contain not more than about 65%,preferably about 10 to about 60%, and most preferably about 35 to about55% of 1,4- units (1,4- microstructure), and at least about 35%preferably about 40 to about 90% and most preferably about 45 to about65% of 1,2- units (1,2-microstructure).

It should be noted that the foregoing B polymer blocks resulting fromthe hydrogenation of a group of randomly arranged 1,2- and 1,4- units ofpolymerized butadiene in a precursor polymer can also be described asblocks of corresponding random copolymers of ethylene and butene-1,wherein two ethylene units correspond to each hydrogenated 1,4-butadieneunit and one butene-1 unit corresponds to each hydrogenated1,2-butadiene unit. Similarly, two ethylene units in the E polymerblocks correspond to each hydrogenated 1,4-butadiene unit in thecorresponding blocks of the precursor polymer.

Specific block copolymers contemplated under this invention are thetriblock copolymer

    (I.sub.x B.sub.y)-(E.sub.z)-(I.sub.x B.sub.y)              (a)

and the pentablock copolymers

    (I.sub.x)-(E.sub.z)-(B.sub.y)-(E.sub.z)-(I.sub.x)          (b)

and

    (I.sub.x)-(B.sub.y)-(E.sub.z)-(B.sub.y)-(I.sub.x)          (c)

where (I_(x)), (B_(y)) and (E_(z)) are polymer blocks of the polymerizedunits as previously defined, (I_(x) B_(y)) is a random copolymer blockof polymerized I and B units, and x, y and z indicate the averagenumbers of the denoted monomeric units in each block consistent with theweight percentage ranges of these monomer units set out previously.

Also contemplated under the invention are star-branched block copolymerscomprising either 1) a combination of random copolymer blocks (I_(x)B_(y)) and polymer blocks (E_(z)) wherein the free end (i.e., uncoupledend) of each branch of the copolymer is a random copolymer block (I_(x)B_(y)); or 2) a combination of polymer blocks (I_(x)), (B_(y)) and(E_(z)) wherein the free end of each branch is a polymer block (I_(x)).The number of monomeric units in each block is consistent with theweight percentage ranges of these units set out previously.

The invention also encompasses the selective hydrogenation of theprecursors of the foregoing polymers such that substantially all of theresidual double bonds of the precursor polybutadiene blocks of the B andE polymer blocks, or the polymerized butadiene units of the IB randomcopolymer blocks are hydrogenated while sufficient unsaturation remainsin the I polymer blocks or the I units of the IB random copolymer blocksto provide a basis for subsequent vulcanization or cross-linking. Theprecursor block polymers and the vulcanized or cross-linked polymers arealso included within the scope of the invention.

Finally, the invention includes processes for the preparation of theforegoing block copolymers using techniques of anionic polymerization.

The selectively hydrogenated block copolymers of this invention containsufficient unsaturation in the terminal blocks so that they may beadequately vulcanized to provide near network perfection with theresulting superior mechanical properties at both room and elevatedtemperatures, while the substantially complete lack of ethylenicunsaturation in the middle or interior blocks provides for a high degreeof oxidative, thermal and pyrolyric stability. Moreover, the high degreeof crystallinity of the interior E polymer blocks provide for highergreen strength and the elimination or reduction of cold flow of thepolymer before vulcanization. Subsequent vulcanization or cross-linkingof the selectively hydrogenated polymer results in a further improvementin properties, e.g., high elongation and elasticity at room and elevatedtemperatures and excellent aging characteristics.

DETAILED DESCRIPTION OF THE INVENTION General

In the block copolymers of this invention, including triblock copolymer(a), i.e.,

    (I.sub.x B.sub.y)-(E.sub.z)-(I.sub.x B.sub.y)              (a)

and the pentablock copolymers (b) and (c), i.e.,

    (I.sub.x)-(E.sub.z)-(B.sub.y)-(E.sub.z)-(I.sub.x)          (b)

and

    (I.sub.x)-(B.sub.y)-(E.sub.z)-(B.sub.y)-(I.sub.x)          (c)

and the star-branched block copolymers comprising either (1) acombination of (I_(x) B_(y)) and (E_(z)) blocks wherein each branchcontains an outermost (I_(x) B_(y)) block; or a combination of (I_(x))(B_(y)) and (E_(z)) blocks wherein each branch contains an outermost(I_(x)) block, the I units prior to any hydrogenation are at least onepolymerized conjugated diene having at least five (5) carbon atoms andthe following formula ##STR1## wherein R¹ -R⁶ are each hydrogen or ahydrocarbyl group, provided that at least one of R¹ -R⁶ is a hydrocarbylgroup, and further provided that the structure of the residual doublebond in the polymerized block I has the following formula ##STR2##wherein R^(I), R^(II), R^(III) and R^(IV) are each hydrogen or ahydrocarbyl group, provided that either both R^(I) and R^(II) arehydrocarbyl groups or both R^(III) and R^(IV) are hydrocarbyl groups;

the B units represent hydrogenated 1,2- and 1,4-butadiene units asdefined hereinbefore, wherein the structure of the residual double bondsprior to hydrogenation are as indicated in the following formulae:##STR3## the E units represent preponderantly straight chain ethyleneunits resulting from the selective hydrogenation of a polybutadieneblock in the precursor polymer which may be composed of at least about802 of 1,4-units. (Up to 20% of the latter polybutadiene blocks in theprecursor polymer may be composed of 1,2-units which on selectivehydrogenation are converted to polymerizod butone-1 units.) In each ofthe foregoing block copolymers, the average total molecular number ofpolymerized I units, i.e., 2× in block copolymers (a), (b) and (c), andthe average molecular total in all the branches of the contemplatedstar-branched block copolymers, per 100,000 M.W., i.e., per 100,000 ofthe total molecular weight of the block copolymer, is, for example,about 15 to 735, preferably about 30 to 370, and more preferably about30 to 150; the average total molecular number of polymerized butadiene(B) units, i.e., y in block copolymer (b), 2y in block copolymers (a)and (c), and the molecular total in all the branches of the contemplatedstar-branched block copolymers per 100,000 M.W. is, for example, about370 to 1815, preferably about 740 to 1815, and more preferably about1111 to 1815 per 100,000 M.W., and the average total molecular number ofE units (ethylene and any butene-1 units present as a result of thepresence of 1,2-polymerized butadiene units in the corresponding blocksof the precursor polymer), i.e., z in block copolymers (a) and (c), 2zin block copolymer (b), and the molecular total in all the branches ofthe contemplated star-branched block copolymers per 100,000 M.W. is, forexample, about 37 to 1111, preferably about 74 to 1111, and morepreferably about 148 to 1111. It should be noted that if the couplingtechnique is used to prepare the precursors of block copolymers (a), (b)and (c), then the average values of x, y and z will be the same for eachblock where two blocks composed of the applicable polymerized units arepresent in the copolymer. However, if a sequential polymerizationtechnique is used, then the average value of x, y and/or z may besomewhat different for each of the two blocks containing the applicablepolymerized units in any particular copolymer.

In the residual double bond of formula (2) R^(I), R^(II), R^(III) andR^(IV) may all be hydrocarbyl groups. The structures of the residualdouble bonds in the I units defined by formula (2) and in polymerizedbutadiene are necessary to produce precursor copolymers which can beselectively hydrogenated in the manner described herein to produce theselectively hydrogenated block copolymers of this invention.

The hydrocarbyl group or groups in the formulae (1) and (2) are the sameor different and they are substituted or unsubstituted alkyl, alkenyl,cycloalkyl, cycloalkenyl, aryl, alkaryl or aralkyl groups or any isomersthereof. Suitable hydrocarbyl groups are alkyls of 1-20 carbon atoms,alkenyls of 1-20 carbon atoms, cycloalkyls of 5-20 carbon atoms,cycloalkenyls of 5-20 carbon atoms, aryls of 6-12 carbon atoms, alkarylsof 7-20 carbon atoms or aralkyls of 7-20 carbon atoms. Examples ofsuitable alkyl groups are methyl, ethyl, propyl, butyl, pentyl, hexyl,heptyl, octyl, decyl, methyldecyl or dimethyldecyl. Examples of suitablealkenyl groups are ethenyl, propenyl, butenyl, pentenyl or hexenyl.Examples of suitable cycloalkyl groups are cyclohexyl ormethylcyclohexyl. Examples of suitable cycloalkenyl groups are 1-, 2-,or 3-cyclohexenyl or 4-methyl-3-cyclohexenyl. Examples of suitable arylgroups are phenyl or diphenyl. Examples of suitable alkaryl groups are4-methylphenyl (p-tolyl) or p-ethylphenyl. Examples of suitable aralkylgroups are benzyl or phenethyl. Suitable conjugated dienes of formula(1) used to polymerize the I polymer or random IB copolymer blocks areisoprene, 2,3-dimethylbutadiene, myrcene, 2-phenyl-1,3-butadiene,2-hexyl-1,3-butadiene, 2-benzyl-1,3-butadiene, 2-p-tolyl-1,3-butadieneor mixtures thereof, preferably isoprene, myrcene or2,3-dimethylbutadiene, and most preferably isoprene.

The weight average molecular weight (M_(w)) of the block copolymers ofthis invention may be, for example, in the range of about 30K to 1.5×10⁶where K=1000), preferably about 60K to 10⁶, and more preferably about75K to 500K, while the number average molecular weight (M_(n)) may be,for example, in the range of about 20K to 10⁶ preferably about 40K to750K, and more preferably about 75K to 500K.

Although the block copolymers of this invention have been exemplified bytriblock copolymer (a), and pentablock copolymers (b) and (c) asdescribed hereinbefore, such block copolymers may contain a largernumber of blocks as long as one of the two conditions of the inventionare met, viz., I) that the terminal blocks are random IB copolymer andthat there is at least one middle or interior E polymer block, or 2)that there are terminal I polymer blocks and at least one each ofinterior B polymer and E polymer blocks. Such copolymers with a largernumber of blocks may contain I polymer or random IB polymer blocks inthe interior of the backbone of a linear copolymer or the branches of astar-branched copolymer so as to allow cross-linking to take place inthe interior as well as the ends of the backbone or branches, with acontrolled large distance between the cross-links of the blockcopolymer. However, the described triblock copolymer (a) and pentablockcopolymers (b) and (c) are preferred. In any case, it is important tohave the block copolymer terminated at each end with the I polymer or IBrandom copolymer blocks to assure that there are unsaturated groups ateach end of the block copolymer enabling the block copolymer to becross-linked or functionalized at the terminal ends thereof. The term"functionalized" is used herein to describe chemical modifications ofthe unsaturated groups to produce functional groups, the nature of whichis described in detail below. The cross-linking of the functionalizedand nonfunctionalized copolymer chains is conducted in a conventionalmanner and is described below.

As is apparent from the foregoing description, the contemplated blockcopolymers of this invention are obtained by selectively hydrogenatingan unhydrogenated precursor block copolymer containing either 1)terminal I polymer blocks which retain some of their saturation afterselective hydrogenation, interior blocks of polybutadiene comprising amixture of 1,4- and 1,2-units as previously described which may besubsequently hydrogenated to the substantially saturated B polymerblocks, and interior blocks of polybutadiene containing at least 80% of1,4-units which on subsequent selective hydrogenation yield thesubstantially saturated E polymer blocks, such unhydrogenated blockcopolymers being the precursors, for example, of pentablock copolymers(b) and (c); or 2) terminal blocks of a random copolymer of an I dieneand butadiene wherein the polymerized butadiene units comprise a mixtureof 1,4- and 1,2-units as previously described and the polymerized Iunits retain some of their unsaturation after selective hydrogenation,and at least one interior block of polybutadiene comprising at least 80%of 1,4-units which on selective hydrogenation yield the substantiallysaturated E polymer blocks, such unhydrogenated block copolymer beingthe precursor, for example, of triblock copolymer (a).

On being subjected to a selective hydrogenation reaction, thepolymerized butadiene units of the precursor block copolymer arehydrogenated to such an extent that they contain substantially none ofthe original unsaturation, while the polymerized I units retain asufficient amount of their original unsaturation to vulcanize or curethe block copolymer. Generally, for a block copolymer wherein the Iunits are polymerized from any of the monomers discussed above, theIodine Number for the I units after the selective hydrogenation reactionis about 10 to about 100%, preferably about 25 to about 100%, morepreferably about 50 to about 100%, and most preferably about 100% of theIodine Number prior to the selective hydrogenation reaction, and for theB and E polymer blocks, it is about 0 to about 10%, preferably about 0to about 0.5%, of the Iodine Number prior to the selective hydrogenationreaction. The Iodine Number, as is known to those skilled in the art, isdefined as the theoretical number of grams of iodine which will add tothe unsaturation in 100 grams of olefin and is a quantitativemeasurement of unsaturation.

In the block copolymers of the invention, the microstructure of thepolymerized I units is not critical and may consist of any combinationof 1,2-, 3,4- and 1,4-units, schematically represented below forpolyisoprene blocks. When a polar compound is used during thepolymerization of the I diene, the polymerized I units compriseprimarily (at least about 80%) 3,4-units, the remainder being primarily(about 20%) 1,2-units; when the polar compound is not used during thepolymerization of the I diene, the polymerized I units compriseprimarily (about 80%) 1,4-units, the remainder being primarily 1,2- and3,4-units.

When I is isoprene, the polymerized units are as follows: ##STR4##

As discussed above, the microstructure of the B polymer blocks should bea mixture of 1,4- and 1,2-units indicated hereinbefore, since thehydrogenation of too high a proportion of 1,4-microstructures producesan amount of crystalline polyethylene which is larger than desired inthese blocks. The microstructure of the I and B polymer blocks in theembodiments utilizing such blocks (as well as of the polymerized Idienes or butadiene in any polymers of this invention) is controlled ina conventional manner, e.g., by controlling the amount and nature of thepolar compounds used during the polymerization reaction, and thereaction temperature. In one particularly preferred embodiment, the Bpolymer block contains about 55% of the 1,2- and about 45% wt. of the1,4-microstructure. The hydrogenation of the polybutadiene blockscontaining about 50 to about 60% wt. of the 1,2- microstructure contentproduces an elastomeric interior block which is substantially anethylene-butene-1 copolymer having substantially no crystallinity.

The terms 1,2-, 1,4-, and 3,4-microstructure or units as used in thisapplication refer to the products of polymerization obtained,respectively, by the 1,2-, 1,4- and 3,4-, additions of monomer unitsinto the growing polymer chain.

The polymerized 1,4- and 1,2-butadiene units of the precursor polymersof this invention are selectively hydrogenated as shown herein muchfaster than the polymerized conjugated dienes of formula (1), e.g., theI units. Thus the disubstituted double bonds of the 1,4-polybutadieneunits are hydrogenated along with the monosubstituted double bonds ofthe 1,2-polybutadiene units, while the disubstituted double bonds of,for example, 3,4-polyisoprene units are hydrogenated at a much slowerrate than the aforementioned butadienes and little or no hydrogenationof the trisubstituted 1,4-polyisoprene units occurs under the conditionsof selective hydrogenation disclosed herein. Furthermore, this isunexpected in view of the teachings of Hoxmeier, Published EuropeanPatent Application, Publication No. 0 315 280, previously cited, whodiscloses that the disubstituted double bonds of the 1,4-polybutadieneunits, monosubstituted double bonds of the 1,2-polybutadiene units anddisubstituted double bonds of the 3,4-polyisoprene units arehydrogenated simultaneously at substantially similar rates, since theycontain Type I unsaturation. It is noted that for block copolymerscontaining polyisoprene and polybutadiene blocks, Fourier transforminfrared (FTIR) analysis of selectively hydrogenated polymers indicatesthat the hydrogenation of the double bonds of the 1,2-polybutadieneunits proceeds most rapidly, followed by the hydrogenation of the doublebonds of the 1,4-polybutadiene units. Infrared absorptions caused bythese groups disappear prior to appreciable hydrogenation of thepolyisoprene units.

As stated, after the precursor block copolymer is prepared, it issubjected to a selective hydrogenation reaction to hydrogenate primarilythe polymerized butadiene units of each of the interior polybutadieneblocks or the terminal random IB copolymer blocks. The selectivehydrogenation reaction and the catalyst are described in detail below.After the hydrogenation reaction is completed, the selectivehydrogenation catalyst is removed from the block copolymer, and thepolymer is isolated by conventional procedures, e.g., alcoholflocculation, steam stripping of solvent or non-aqueous solventevaporation. An anti-oxidant, e.g., Irganox 1076 (from Ciba-Geigy), isnormally added to the polymer solution prior to polymer isolation.

The isolated polymer is vulcanizable through the unsaturated end units Iby a number of well known processes utilized currently for thermosettinghydrocarbon elastomers. Such processes are detailed in RUBBERTECHNOLOGY, THIRD EDITION, VAN NOSTRAND REINHOLD COMPANY, New York,1987, Maurice Morton, Editor, chapters 2,9 and 10, incorporated hereinby reference.

As stated, the star-branched block copolymers of this invention compriseeither 1) a combination of random copolymer blocks (I_(x) B_(y)) andpolymer blocks (E_(z)) wherein the free end (i.e., uncoupled end) ofeach branch of the copolymer is a random copolymer block (I_(x) Y B );or 2) a combination of polymer blocks (I_(x)), (B_(y)) and (E_(z))wherein the free end of each branch is a polymer block (I_(x)). Sinceeach branch of the star-branched copolymer has only a single end, theadvantages of the invention obtained as a result of unsaturatedpolymerized I units in the terminal blocks may be obtained by utilizinghalf the structure of triblock polymer (a) or pentablock polymers (b)and (c) as each branch of the star-branched polymer. Thus, one type ofpreferred polymer has branches composed of two blocks, viz., anoutermost random IB copolymer block and an interior E polymer block; asecond preferred branch has branches composed of three blocks, viz., anoutermost I polymer block, a central B polymer block and an innermost Epolymer block; and a third preferred polymer has branches also composedof three blocks, viz., an outermost I polymer block, a central E polymerblock and an innermost B polymer block. The relative percentages and theranges of numbers of each type of unit, viz., the total sums of each ofx, y and z, are similar to the values for the preferred triblockcopolymer (a) and pentablock copolymers (b) and (c) previouslydescribed. Furthermore, the selective hydrogenation and resultingreduction in iodine numbers of the star-branched block copolymers arealso similar to those of linear polymers (a), (b) and (c) set outhereinbefore.

The block copolymers of this invention having a particularly largenumber of polymerized I units in the terminal I polymer or IB randomcopolymer blocks (i.e., containing 100-200 monomer units) have anincreased vulcanization rate, as compared to those containing a smallernumber of I units in the terminal blocks, and are co-vulcanizable withdiene rubbers available in the art, e.g., polybutadiene and naturalrubbers. The block polymers containing such large I blocks can beblended with diene rubbers by conventional methods and subsequentlyvulcanized to produce novel compositions of this invention. Theresulting materials are expected to have increased oxidation and ozonedegradation resistance as compared to known diene rubbers alone, andtherefore are expected to be valuable materials for the production ofwhite sidewalls of tires and similar articles.

In all embodiments of the invention, mixtures of I conjugated dienes maybe used to form the I polymer blocks or the IB random copolymer blocksof the contemplated block copolymers. Accordingly, whenever a referenceis made herein to an I conjugated diene, it may encompass more than oneof such type of monomer or polymerized monomeric unit.

While the block copolymers of this invention have been describedprimarily in terms of polymerized I, B and E units in the variousblocks, it is to be understood that controlled minor amounts of othermonomers may be used when preparing the precursors of such blocks. Thus,a minor amount (e.g., about 0.1 to about 30 mole %) of anaryl-substituted olefin, e.g., styrene or other suitable monomers (suchas alkylated styrene, vinyl naphthalene or alkylated vinyl naphthalene),may be incorporated in the I, B or random IB blocks for further controlof glass transition temperature (Tg), density, solubility parameters andrefractive index. Similarly, the scope of this embodiment alsoencompasses polymers wherein the various blocks may be comprised of thedescribed polymers of an I diene, butadiene, or a mixture of an I dieneand butadiene, and a minor amount of any other anionically polymerizablemonomer capable of polymerizing with such indicated monomers.

It will be apparent to those skilled in the art that proper choice ofpolymerization parameters can produce polymers with a great variety ofcompositional and structural differences, falling within the scope ofour invention. For example, changes in composition of the interior B andE polymer blocks or the polymerized B units in the random IB copolymerblocks control the nature of the rubbery properties while changes in theI polymer terminal blocks or the polymerized I units in the IB randomcopolymer terminal blocks permit response to different vulcanizingagents, e.g., sulfur-based cure systems and phenolic resin cure systems.

Blends Of Inventive Polymers With Other Materials

The block copolymers of this invention can be blended with otherrubbers, in which case the degree of unsaturation of the copolymers ofthe invention can be adjusted so that the vulcanization rate of the twomaterials is substantially the same. Suitable rubbers which can beblended with the copolymers of this invention are EPDM, butyl rubber andrubbers based on butadiene or isoprene.

The block copolymers of this invention can also be blended withplastics, e.g., isotactic polypropylene, polystyrene, polyethylene,Nylon, polycarbonates, polyesters and styrene-acrylonitrile resins.Thermoplastic elastomers having excellent properties can be obtained bydynamically vulcanizing a blend of polypropylene and the elastomers ofour invention, in which the elastomers are cross-linked to a very highdegree. A commercial material, Santoprene (trademark of and produced byMonsanto Chemical Co.) is based upon blends of polypropylene and EPDM.Details of the preparation and properties of such blends are presentedin THERMOPLASTIC ELASTOMERS, A COMPREHENSIVE REVIEW, edited by N. R.Legge et al., Chapter 7, Hanser Publishers, Munich, Vienna and New York(1987), the contents of which are incorporated herein by reference. Suchdynamically vulcanized blends prepared with the polymers of theinvention in a conventional manner, e.g., that of N. R. Legge et al.,wherein the polymers of this invention are blended with polypropylene,and most particularly wherein the linear triblock and pentablockpolymers of this invention are blended with polypropylene, can providethermoplastic elastomers with unique elastomeric properties.

The block copolymers of this invention can be compounded withingredients known to those skilled in the art, e.g., fillers such assilica, carbon black, extender oils, anti-oxidants, tackifying agents,vulcanizing agents and similar materials.

Polymerization Reaction

The precursor block copolymers of this invention are polymerized by ananionic polymerization process. Anionic polymerization is well known inthe art, and it is utilized in the production of a variety of commercialpolymers. An excellent comprehensive review of the anionicpolymerization processes appears in the text ADVANCES IN POLYMER SCIENCE56, ANIONIC POLYMERIZATION, pp. 1-90, Springer-Verlag, Berlin,Heidelberg, New York, Tokyo 1984 in a monograph entitled ANIONICPOLYMERIZATION OF NON-POLAR MONOMERS INVOLVING LITHIUM, by R. N. Young,R. P. Quirk and L. J. Fetters, incorporated herein by reference. Theanionic polymerization process is conducted in the presence of asuitable anionic catalyst (also known as an initiator), such asn-butyl-lithium, sec-butyl-lithium, t-butyl-lithium, sodium naphthalideor cumyl potassium. The amount of the catalyst and the amount of themonomer in the polymerization reaction dictate the molecular weight ofthe polymer. The polymerization reaction is conducted in solution usingan inert solvent as the polymerization medium, e.g., aliphatichydrocarbons, such as pentane, hexane, cyclohexane or heptane, oraromatic solvents, such as benzene or toluene.

The process, when using a lithium-based catalyst, comprises forming asolution of the isoprene monomer in an inert hydrocarbon solvent, suchas cyclohexane. At some point in the process, and necessarily before theformation of the B block or random IB copolymer blocks, the catalyst ismodified by the addition of one or more polar compounds selected fromthe group consisting of ethers, thioethers and tertiary amines, e.g.,tetrahydrofuran. The polar compound is necessary to control themicrostructure of the B polymer interior blocks, or the polymerized Bunits of the random IB copolymer blocks, i.e., the content of the1,2-structure therein. The higher the content of the polar compounds,the higher will be the content of the 1,2-structure of the polymerizedbutadiene in these blocks. Since the presence of the polar compound isnot essential in the formation of the I polymer blocks with manyinitiators unless a high 3,4-structure content of the first block isdesired, it is not necessary to introduce the polar compound at thisstage, since it may be introduced just prior to or together with theaddition of the butadiene in forming the B polymer blocks later in thereaction. Examples of polar compounds which may be used aretetrahydrofuran (THF) 1,2-diethoxyethane, dimethyl ether, diethyl ether,ethyl methyl ether, ethyl propyl ether, dioxane, diphenyl ether,tripropyl amine, tributyl amine, trimethyl amine, triethyl amine, andN-,N-,N'-,N'-tetramethyl ethylene diamine. Mixtures of the polarcompounds may also be used. The amount of the polar compound depends onthe type of the polar compound and the polymerization conditions as willbe apparent to those skilled in the art. The effect of the polarcompounds on the polybutadiene microstructure is detailed in ANTKOWIAKet al., TEMPERATURE AND CONCENTRATION EFFECTS ON POLAR-MODIFIED ALKYLLITHIUM POLYMERIZATIONS AND COPOLYMERIZATIONS, JOURNAL OF POLYMERSCIENCE: Part A-1, Vol. 10, 1319-1334 (1972), incorporated herein byreference. The polar compounds also accelerate the rate ofpolymerization.

In forming, for example, pentablock copolymer (b), an alkyllithium-based initiator and an I diene, e.g., isoprene, monomer arecombined in an inert solvent in the absence of a polar compound, andpolymerization of the isoprene proceeds to produce the first terminalblock whose molecular weight is determined by the ratio of the isopreneto the initiator. The "living" polyisoprenyl anion formed in this firststep is utilized as the catalyst for further polymerization. At thistime, butadiene monomer is introduced into the system and blockpolymerization of the second block proceeds, the absence of the polarcompound now causing this polybutadiene block to be substantiallylimited to the 1,4-structure which is the precursor of the desired Epolymer block. The resulting product is a living diblock polymer havinga terminal anion and a lithium counterion. The living diblock polymerserves as a catalyst for the growth of the central B polymer block,formed when butadiene monomer is added to the reaction vessel togetherwith a polar compound to produce a polybutadiene (B) block made up ofboth 1,4- and 1,2-units, and containing the anion of the resultingliving triblock copolymer. The living triblock anion is then coupledwith an appropriate coupling agent to form a precursor pentablockcopolymer which may be selectively hydrogenated to form block copolymer(b) containing E polymer blocks. The polymerization reaction is usuallyconducted at a temperature of between 0° C. and about 100° C., althoughhigher temperatures can be used. Control of a chosen reactiontemperature is desirable since it can influence the effectiveness of thepolar compound additive in controlling the polymer microstructure. Thereaction temperature can be, for example, from 50° to 80° C. Thereaction pressure is not critical and varies from atmospheric to about100 psig.

In forming block copolymer (c) under this invention, an initial polymerblock of an I diene, e.g., isoprene, is first formed by contacting suchI diene with an anionic catalyst either in the absence of a polarcompound, in which case the I diene polymer block is composed mainly of1,4-units, or in the presence of a polar compound in which case the Idiene polymer block has a high proportion of 3,4-units. To the livingpolymer block is then added butadiene together with a polar compound ifno polar compound was used in the formation of the first, i.e., I diene,polymer block, to form a polybutadiene (B) block containing significantproportions of both 1,4- and 1,2-units as previously defined. The polarcompound is then removed by various means known in the art, e.g., byvacuum distilling, and an additional amount of butadiene is charged tothe reactor forming a third polybutadiene block containing over 80% of1,4-units the living triblock copolymer is then coupled to form apentablock copolymer containing terminal polyisoprene blocks, adjacentto which are polybutadiene blocks containing 1,4- and 1,2-units and acentral 1,4-polybutadiene block which is the precursor of an E polymerblock. This precursor polymer is then selectively hydrogenated to obtainblock copolymer (c).

Triblock copolymer (a) may be prepared by contacting with an anioniccatalyst in the presence of a polar compound a mixture of sufficientamounts of conjugated diene I and butadiene to form a living block ofrandom IB copolymer, the polymerized butadiene units of which arecomposed of no more than about 65% of 1,4-units and at least about 35%of 1,2-units. Most of the polar compound is then removed from thereaction mixture, and an additional amount of butadiene is added to forma living diblock composed of a random IB copolymer block, and at theother end, a polybutadiene block composed of at least about 80% ofpolymerized 1,4-units. The living diblock is then coupled in thepresence of a coupling agent as described to produce a precursortriblock copolymer, which may be selectively hydrogenated to formtriblock copolymer (a).

The substitution of myrcene for the isoprene during the polymerizationof the I polymer block insures the incorporation of a high proportion oftrisubstituted double bonds, even in the presence of polar compoundssince myrcene contains a pendant trisubstituted double bond which is notinvolved in the polymerization process. In a coupling process similar tothat described above, block polymers containing polyisoprene end blocks(or any other polymerized monomer suitable for use in the I polymerblock) having a high 3,4-microstructure content can be obtained byadding the polar compound prior to the isoprene (or other monomer)polymerization.

The use of the coupling technique for the production of triblock andpentablock polymers greatly reduces the reaction time necessary for thecompletion of polymerization, as compared to a sequential addition ofmonomers utilized to prepare each block. Such coupling techniques arewell known and utilize coupling agents, such as esters, CO₂, iodine,dihaloalkanes, silicon tetrachloride, divinyl benzene,alkyltrichlorosilanes and dialkyldichlorosilanes. The use of tri- ortetra-functional coupling agents, such as alkyltrichlorosilanes orsilicon tetrachloride, permits the formation of macromolecules having 1-or 2- main chain branches, respectively. The addition of divinyl benzeneas a coupling agent has been documented to produce molecules having upto 20 or more separately joined segments.

The use of some of the coupling agents provides a convenient means ofproducing star-branched block polymers. The star-branched block polymersare made from any combination of blocks I, B and E or random IB and E,discussed above, providing that each free end (i.e., uncoupled end) ofthe star-branched polymer is either an I or a random IB block,respectively. The molecular weight of the star-branched block copolymerswill depend on the number of branches in each such copolymer, as will beapparent to those skilled in the art.

Suitable coupling agents and reactions are disclosed in the followingreferences which are incorporated herein by reference: U.S. Patents3,949,020; 3,594,452; 3,598,887; 3,465,065; 3,078,254; 3,766,301;3,632,682; 3,668,279; and British patents 1,014,999; 1,074,276;1,121,978.

Selective Hydrogenation

The precursor block copolymer is selectively hydrogenated to saturatethe interior polybutadiene blocks of each of the pentablocks. The methodof selectively hydrogenating the polybutadiene block is similar to thatof Falk, "Coordination Catalysts For The Selective Hydrogenation ofPolymeric Unsaturation", JOURNAL OF POLYMER SCIENCE: PART A-1, Volume 9,2617-2623 (1971), and may be conducted with the novel hydrogenationcatalyst and process used herein. Any other known selectivehydrogenation methods may also be used, as will be apparent to thoseskilled in the art, but it is preferred to use the method describedherein. In summary, the selective hydrogenation method preferably usedherein comprises contacting the previously prepared block copolymer withhydrogen in the presence of the novel catalyst composition.

The novel hydrogenation catalyst composition and hydrogenation processare described in detail in application Ser. No. 07/466,136, filedJanuary 16, 1990, by T. S. Coolbaugh et al. The hydrogenation catalystcomposition is synthesized from at least one transition metal compoundand an organometallic reducing agent.

Suitable transition metal compounds are compounds of metals of GroupIVb, Vb, VIb, or VIII, preferably IVb or VIII of the Periodic Table ofthe Elements, published in LANGE's HANDBOOK OF CHEMISTRY (13th Edition,1985, McGraw-Hill Book Company, New York, John A. Dean, Editor).Non-limiting examples of such compounds are metal halides, e.g.,titanium tetrachloride, vanadium tetrachloride; vanadium oxytrichloride,titanium and vanadium alkoxides, wherein the alkoxide moiety has abranched or unbranched alkyl radical of 1 to about 20 carbon atoms,preferably 1 to about 6 carbon atoms. Preferred transition metalcompounds are metal carboxylates or alkoxides of Group IVb or VIII ofthe Periodic Table of the Elements, such as nickel (II)2-ethylhexanoate, titanium isopropoxide, cobalt (II) octoate, nickel(II) phenoxide and ferric acetylacetonate.

The organometallic reducing agent is any one or a combination of any ofthe materials commonly employed to activate Ziegler-Natta olefinpolymerization catalyst components containing at least one compound ofthe elements of Groups Ia, IIa, IIb, IIIa, or IVa of the Periodic Tableof the Elements. Examples of such reducing agents are metal alkyls,metal hydrides, alkyl metal hydrides, alkyl metal halides, and alkylmetal alkoxides, such as alkyllithium compounds, dialkylzinc compounds,trialkylboron compounds, trialkylaluminum compounds, alkylaluminumhalides and hydrides, and tetraalkylgermanium compounds. Mixtures of thereducing agents may also be employed. Specific examples of usefulreducing agents include n-butyl-lithium, diethylzinc, di-n-propylzinc,triethylboron, diethylaluminumethoxide, triethylaluminum,trimethylaluminum, triisobutylaluminum, tri-n-hexylaluminum,ethylaluminum dichloride, dibromide, and dihydride, isobutyl aluminumdichloride, dibromide, and dihydride, diethylaluminum chloride, bromide,and hydride, di-n-propylaluminum chloride, bromide, and hydride,diisobutylaluminum chloride, bromide and hydride, tetramethylgermanium,and tetraethylgermanium. Organometallic reducing agents which arepreferred are Group IIIa metal alkyls and dialkyl metal halides having 1to about 20 carbon atoms per alkyl radical. More preferably, thereducing agent is a trialkylaluminum compound having 1 to about 6 carbonatoms per alkyl radical. Other reducing agents which can be used hereinare disclosed in Stevens et al., U.S. Pat. No. 3,787,384, column 4, line45 to column 5, line 12 and in Strobel et al., U.S. Pat. No. 4,148,754,column 4, line 56 to column 5, line 59, the entire contents of both ofwhich are incorporated herein by reference. Particularly preferredreducing agents are metal alkyl or hydride derivatives of a metalselected from Groups Ia, IIa and IIIa of the Periodic Table of theElements, such as n-butyl-lithium, sec-butyl-lithium, n-hexyl-lithium,phenyl-lithium, triethylaluminum, tri-isobutylaluminum,trimethylaluminum, diethylaluminum hydride and dibutylmagnesium.

The molar ratio of the metal derived from the reducing agent to themetal derived from the transition metal compound will vary for theselected combinations of the reducing agent and the transition metalcompound, but in general it is about 1:1 to about 12:1, preferably about1.5:1 to about 8:1, more preferably about 2:1 to about 7:1 and mostpreferably about 2.5:1 to about 6:1. It will be apparent to thoseskilled in the art that the optimal ratios will vary depending upon thetransition metal and the organometallic agent used, e.g., for thetrialkylalumium/nickel(II) systems the preferred aluminum: nickel molarratio is about 2.5:1 to about 4:1, for the trialkylaluminum/cobalt(II)systems the preferred aluminum: cobalt molar ratio is about 3:1 to about4:1 and for the trialkylaluminum/titanium(IV) alkoxides systems, thepreferred aluminum: titanium molar ratio is about 3:1 to about 6:1.

The mode of addition and the ratio of the reducing agent to thetransition metal compound are important in the production of the novelhydrogenation catalysts having superior selectivity, efficiency andstability, as compared to prior art catalytic systems. During thesynthesis of the hydrogenation catalysts it is preferred to maintain themolar ratio of the reactants used to synthesize the catalystsubstantially constant. This can be done either by the addition of thereducing agent as rapidly as possible to a solution of the transitionmetal compound, or by a substantially simultaneous addition of theseparate streams of the reducing agent and the transition metal compoundto a catalyst synthesis vessel in such a manner that the selected molarratios of the metal of the reducing agent to the metal of the transitionmetal compound are maintained substantially constant throughoutsubstantially the entire time of addition of the two compounds. The timerequired for the addition must be such that excessive pressure and heatbuild-up are avoided, i.e., the temperature should not exceed about 80°C. and the pressure should not exceed the safe pressure limit of thecatalyst synthesis vessel.

In a preferred embodiment, the reducing agent and the transition metalcompound are added substantially simultaneously to the catalystsynthesis vessel in such a manner that the selected molar ratio of thereducing agent to the transition metal compound is maintainedsubstantially constant during substantially the entire time of theaddition of the two compounds. This preferred embodiment permits thecontrol of the exothermic reaction so that the heat build-up is notexcessive, and the rate of gas production during the catalyst synthesisis also not excessive; accordingly, the gas build-up is relatively slow.In this embodiment, carried out with or without solvent diluent, therate of addition of the catalyst components is adjusted to maintain thesynthesis reaction temperature at or below about 80° C., which promotesthe formation of the selective hydrogenation catalyst. Furthermore, theselected molar ratios of the metal of the reducing agent to the metal ofthe transition metal compound are maintained substantially constantthroughout the entire duration of the catalyst preparation when thesimultaneous mixing technique of this embodiment is employed.

In another embodiment, the catalyst is formed by the addition of thereducing agent to the transition metal compound. In this embodiment, thetiming and the order of addition of the two reactants is important toobtain the hydrogenation catalyst having superior selectivity,efficiency and stability. Thus, in this embodiment, it is important toadd the reducing agent to the transition metal compound in that order inas short a time period as practically possible. In this embodiment, thetime allotted for the addition of the reducing agent to the transitionmetal compound is critical for the production of the catalyst. The term"as short a time period as practically possible" means that the time ofaddition is as rapid as possible, such that the reaction temperature isnot higher than about 80° C. and the reaction pressure does not exceedthe safe pressure limit of the catalyst synthesis vessel. As will beapparent to those skilled in the art, that time will vary for eachsynthesis and will depend on such factors as the types of the reducingagents, the transition metal compounds and the solvents used in thesynthesis, as well as the relative amounts thereof, and the type of thecatalyst synthesis vessel used. For purposes of illustration, a solutionof about 15 ml of triethylaluminum in hexane should be added to asolution of nickel(II) octoate in mineral spirits in about 10-30seconds. Generally, the addition of the reducing agent to the transitionmetal compound should be carried out in about 5 seconds (sec) to about 5minutes, depending on the quantities of the reagents used. If the timeperiod during which the reducing agent is added to the transition metalcompound is prolonged, e.g., more than 15 minutes, the synthesizedcatalyst is less selective, less stable and may be heterogeneous.

In the embodiment wherein the reducing agent is added as rapidly aspossible to the transition metal compound, it is also important to addthe reducing agent to the transition metal compound in theaforementioned sequence to obtain the novel catalyst. The reversal ofthe addition sequence, i.e., the addition of the transition metalcompound to the reducing agent, or the respective solutions thereof, isdetrimental to the stability, selectivity, activity and homogeneity ofthe catalyst and is therefore undesirable.

In all embodiments of the hydrogenation catalyst synthesis, it ispreferred to use solutions of the reducing agent and the transitionmetal compound in suitable solvents, such as hydrocarbon solvents, e.g.,cyclohexane, hexane, pentane, heptane, benzene, toluene or mineral oils.The solvents used to prepare the solutions of the reducing agent and ofthe transition metal compound may be the same or different, but if theyare different, they must be compatible with each other so that thesolutions of the reducing agent and the transition metal compound arefully soluble in each other.

The hydrogenation process comprises contacting the unsaturated polymerto be hydrogenated with an amount of the catalyst solution containingabout 0.1 to about 0.5, preferably about 0.2 to about 0.3 mole percentof the transition metal based on moles of the polymer unsaturation. Thehydrogen partial pressure is about 5 psi to about several hundred psi,but preferably it is about 10 to about 100 psi. The temperature of thehydrogenation reaction mixture is about 25 to about 80° C., since highertemperatures may lead to catalyst deactivation. The length of thehydrogenation reaction may be as short as 30 minutes and, as will beapparent to those skilled in the art, depends to a great extent on theactual reaction conditions employed. The hydrogenation process may bemonitored by any conventional means, e.g., infra-red spectroscopy,hydrogen flow rate, total hydrogen consumption, or any combinationthereof.

After the hydrogenation reaction is completed, the hydrogenationcatalyst must be removed from the polymer, for example, by washing twicewith equal volumes of 10% aqueous citric acid solution also containing5% isopropanol at 60° C. The polymer solution is then water washed andthe polymer isolated by conventional methods, e.g., steam or alcoholflocculation or solvent evaporation.

Cross-linking And Functionalization Of The Terminal Blocks

In addition to acting as sites for vulcanization, the unsaturatedterminal blocks of the block polymers of this invention can bechemically modified to provide benefits obtained with similarmodifications of existing commercial materials, such as butyl rubber orEPDM. In some instances, the benefits obtained by a chemicalmodification of butyl rubber or EPDM may be magnified using theelastomers of our invention as a matrix instead of the butyl rubber orEPDM because of their intrinsically superior elastomeric properties.

An example of such a chemical modification of the polymers of thisinvention is sulfonation of the olefinic unsaturation of the polymerizedI units or polymerized dienes of formula (1) of any polymers of thisinvention containing the polymerized I units or polymerized dienes offormula (1), followed by neutralization of the thus formed polymericsulfonic acid with metal ions or amines. When such a modification isperformed on a commercial ethylene-propylene-diene monomer (EPDM)rubber, a thermoplastic elastomer which behaves like a vulcanized rubberat room temperature but can be shaped at higher temperatures isproduced. A description of an example of a process for and productdescription of such a chemically modified EPDM can be found in IONS INPOLYMERS, Advances in Chemistry Series 187, American Chemical Society,Washington, D.C. 1980, pp. 3-53, incorporated herein by reference.Following the procedures used for EPDM described in the aforementionedpublication with the block copolymers of our invention, thermoplasticelastomers with greatly improved elongation properties were prepared.

It is known that the halogenation of the unsaturation in butyl rubber(based upon isoprene monomer) prior to the vulcanization treatment,produces dramatic changes in vulcanization rate and provides greaterversatility in the choice of vulcanizing agents. Since the residualunsaturated groups in the block copolymers of our invention present inthe polymerized I units may also be based on isoprene monomer, thehalogenation of the polymer of this embodiment provides the samebenefits, but with the retention of the greater elongationcharacteristics and resistance to cold flow inherent in the inventionpolymer. The same benefits will be obtained with any other dienes whichcan be used to prepare the I polymer or random IB copolymer blocks ofthe invention, and therefore any polymers of this invention containingany such dienes can be halogenated in the same manner as the butylrubber. Any other polymers of this invention containing the polymerizeddienes of formula (1) or polymerized I units can also be halogenated inthe same manner.

It is also known that the reaction of EPDM with maleic anhydride atelevated temperatures (e.g., about 150° C. to about 250° C.) producesmaleic modified EPDM which is used commercially as an impact modifier,particularly for Nylon. Similar modification of the polymers of anyembodiments of our invention occurs readily, since the residual isopreneunsaturation, primarily of the illustrated 3,4-type, is more reactivewith maleic anhydride than are the internal bonds found in EPDM. Theresultant impact modifier, because of its greater elongation, providessuperior properties when blended with Nylon.

EPDM polymers which have been modified with polar functionality areutilized as dispersant type viscosity index improvers in multigradelubricants. A great number of patents are devoted to such modifications.Any of the modifications performed on EPDM for this purpose can beperformed with the polymers of this invention. Typical modificationswhich can be used with the polymers of this invention are described in:U.S. Pat. Nos. 3,099,644; 3,257,349; 3,448,174; 3,997,487; 3,870,841;3,642,728; 3,847,854; 3,437,556; 4,557,849; 4,032,700; 3,899,434;4,557,847; 4,161,452; 4,170,562; 4,517,104; 4,320,017; 4,502,972;4,098,710; 4,007,121; 4,011,380; 4,033,888; 4,145,298; 4,402,844;4,146,489 and British patent 1,072,796, the disclosures of all of whichare incorporated herein by reference.

The above examples illustrate only some of the potentially valuablechemical modifications of the polymers of this invention. The highmolecular weight block polymers of this invention, providing a means fora wide variety of chemical modifications only at the ends of themolecule (i.e., at the I polymer cr random IB copolymer blocks only),present the opportunity to prepare materials previously impossiblebecause of the lack of availability of such polymers. Some examples ofwell known chemical reactions which can be performed on polymers of thisinvention are found in E. M. FETTES, CHEMICAL REACTIONS OF POLYMERS,High Polymers, Vol. 19, John Wiley, New York, 1964, incorporated hereinby reference.

Our invention provides block hydrocarbon polymers capable of beingvulcanized to a perfect network with a distance between cross-linkssubstantially equivalent to the dimensions of the unvulcanizedelastomeric molecule. In addition to the expected improvements inelastomeric properties, the saturated main chain of the polymers of ourinvention provides a high degree of oxidative and thermal stability.Unique materials can also be obtained by chemical modifications of theblock polymers of this invention, since such modifications can becarried out selectively only at the unsaturated terminal ends of themolecules.

The cross-linking of the selectively hydrogenated block polymers of thisinvention is conducted in a conventional manner by contacting the blockcopolymer with a suitable cross-linking agent or a combination of suchagents. The cross-linking process produces a copolymer having uniformdistance between cross-links.

The block copolymers can also be functionalized by reacting the terminalblocks containing unsaturated groups with various reagents to producefunctional groups, such as hydroxyl, epoxy, sulfonic acid, mercapto,acrylate or carboxyl groups. Functionalization methods are well known inthe art.

The block copolymers, including the star-branched polymers, of thisinvention can be used in a variety of applications, e.g., to produceelectrical insulation, pressure sensitive adhesives, sealants,rubberized asphalts, in automotive applications, e.g., hoses, tubing,weatherstripping, in construction industry, e.g., to produce gaskets,rubber sheeting for roofing, pond and ditch liners, and in many otherapplications.

The following examples further illustrate additional features of theinvention. However, it will be apparent to those skilled in the art thatthe specific reactants and reaction conditions used in the examples donot limit the scope of the invention.

In all of the following examples, the experimental work was performedwith dried reactors and equipment and under strictly anaerobicconditions. Extreme care must be used to exclude air, moisture and otherimpurities capable of interfering with the delicate chemical balanceinvolved in the synthesis of the polymers of this invention, as will beapparent to those skilled in the art.

EXAMPLE 1

This example illustrates the preparation of a polymer which is aprecursor of the type of pentablock copolymer (b), such precursorpolymer having terminal polyisoprene blocks, two short blocks of1,4-polybutadiene interior to the polyisoprene end blocks and exteriorto a central polybutadiene block, which forms the major portion of thepolymer. A procedure was used as described below, whereby thepolyisoprene blocks were predominantly of the 1,4- microstructure, thecentral polybutadiene block was less than 50% of the 1,4- microstructureand the two polybutadiene blocks adjacent to the end blocks containedover 90% of the 1,4-microstructure.

The preparation was carried out under nitrogen atmosphere in a two-quartglass bowled stirred pressure reactor equipped with an air-drivenstirrer, a pressure gauge, a thermometer well, a heat exchange coil, atop surface inlet valve, a dip tube feeder with valve, a syringeinjection port containing a viton rubber gasket and a blow-out disk (200psi). To the reactor were added, in sequence, 1200 mL of drycyclohexane, 12.8 mL (8.72 grams) of isoprene, and 3 mg of dipyridylindicator. The mixture was warmed to 50° C. and titrated with 1.6 molarn-butyl lithium (0.2 mL) to an orange color. After a few minutes 1.7 mLof a 1.7 molar solution (2.89 moles) of t-butyl lithium were added.Polymerization was allowed to proceed for 18 hours, although it isestimated that 4 hours at 50° C. would have been sufficient time tocomplete polymerization of the initial polyisoprene blocks. Next, 5.0grams of butadiene were added and the reaction was allowed to proceed anadditional 5 hours. Two mL of a 1.0 molar solution of 1,2-diethoxyethanein cyclohexane were injected into the reactor, followed by 86 grams ofbutadiene. The diethoxyethane produced a high 1,2- unit content for thispolybutadiene block and dramatically increased the rate ofpolymerization such that the monomer was consumed within an hour. Then,15.48 ml of a 0.28 molar cyclohexane solution (4.33 mmoles) ofphenylbenzoate were added to couple the triblock anion. The mixture wasstirred at 50°-55° C. for an additional 30 minutes. A sample of thepolymer was isolated and analyzed by gel permeation chromatography(GPC). The number average molecular weight (M_(n)) was 73,800.

EXAMPLE 2

This example illustrates the selective hydrogenation of thepolybutadiene blocks in the pentablock copolymer of Example 1.

Pentane in an amount of 200 mL containing 20 grams of dissolvedpentablock polymer as prepared in Example 1 was introduced into a Parrshaker hydrogenation apparatus. This amount of polymer represents 0.32mole of polybutadiene unsaturation. The hydrogenation catalyst wasprepared by adding 10.8 mL of a nickel octoate solution (6% by weightnickel) to a solution of 45.2 millimoles of triethyl aluminum in 102.2mL of hexane. The nickel octoate was added slowly (over about 1 hour)using a syringe pump to give a final catalyst solution which was 0.1molar in nickel and had an Al/Ni molar ratio of 3.6/1. Six mL of thiscatalyst solution were added to the polymer solution in the Parr shaker.The shaker apparatus was purged 4 times with 50 psig hydrogen, pressuredto 50 psig with hydrogen, and heated to 50° C. Temperature wasmaintained at 50° C. and the reaction vessel was shaken for about fourhours. Analysis of an aliquot of the product by FTIR demonstratedcomplete loss of absorption related to the 1,2-butadiene (910 and 994cm⁻¹) and trans 1,4-butadiene (967 cm⁻¹), and NMR analysis showedretention of over 50% of the 1,4-isoprene double bonds originallypresent in the precursor polymer. The reaction mixture was degassed andtreated with 3-4 drops of Jeffamine D-2000 (a polyether diamine) and 1mL of HCl (6N). After stirring for a short time, the dark catalyst colorhad discharged and the solution was added to 200 mL of isopropanolcontaining an anti-oxidant (0.5 g of Irganox 1076). The precipitatedpolymer was isolated and dried in a vacuum oven. Analysis of the polymerindicated that its molecular weight was substantially unchanged and thatessentially no residual nickel was present (less than 1 ppm).

The foregoing selective hydrogenation was found to be effective tosubstantially completely hydrogenate (99.7%) the polybutadiene blocks,including the conversion of the central block substantially to straightchain polyethylene, while allowing sufficient unsaturation in thepolyisoprene blocks so that the polymer could be effectively vulcanized.After such hydrogenation, the molecular weight of the polymer wasessentially unchanged. The unvulcanized polymer had greatly improvedresistance to cold flow due to the crystallinity of the centralpolyethylene block, as compared to a similar polymer but without suchpolyethylene block, i.e., a polyisoprene-polybutadiene-polyisoprenetriblock copolymer wherein the polybutadiene contains a substantialnumber of 1,2-units.

EXAMPLE 3

This example illustrates the preparation of a pentablock copolymer (c)including the precursor pentablock copolymer and its selectivehydrogenation.

Two hundred grams of purified cyclohexane and a small amount (ca. 3 mg)of bipyridyl were introduced into a 600 mL stirred glass reactorequipped with an air-driven stirrer, a pressure gauge, thermocouple, topsurface inlet valve, dip tube feeder with valve, heating-mantle withvariable controller and combination nitrogen/vacuum inlet with valve.Air was removed from the reactor under vacuum and replaced by drynitrogen. Following this, 7.0 mL of isoprene (70 mmol) and 4.0 mL (49.3mmol) of tetrahydrofuran freshly distilled from benzophenone ketyl wereintroduced into the reactor. The temperature of the reactor and itscontents was raised to 50° C. and the solution was titrated by additionof 1.6M butyl lithium until a persistent red color was obtained (0.3mL). Following this, 0.63 mL of 1.6 M butyl lithium (1.01 mmol) wereinjected into the reactor in order to initiate polymerization of theisoprene. The reaction was allowed to run for one hour at 60° C., afterwhich 30.4 g of purified butadiene (0.563 mol) were pressured into thereactor while maintaining a temperature of 60° C. After one hour, thereactor pressure had returned to the level prior to butadiene addition(25 psi) and formation of the second block of the copolymer wascomplete.

About half the solvent was then removed from the reactor by means ofreduced pressure and collected in a trap cooled with Dry Ice. Gaschromatography and nuclear magnetic resonance of the collected solventshowed the presence of a significant amount of THF, thereby indicatingthe successful removal of a substantial percentage of the initial THF.One hundred fifty mL of dry solvent were then reintroduced, via pressurecylinder, into the reactor and 4.8 g of purified butadiene (89 mmol)were introduced. This third block was allowed to polymerize overnight atroom temperature, after which 0.5 millimole of dichlorodimethylsilanewas added to effect coupling to give the desired precursor pentablockpolymer with a central polybutadiene block of low vinyl content, i.e.,containing more than 80% of 1,4-units.

The resultant polymer solution was then selectively hydrogenated. Six mLof Al/Co homogeneous catalyst (Al/Co=3.0,[Co]=0.133M) were added to theabove polymer solution and the mixture was flushed several times withhydrogen, after which the polymer was hydrogenated at 55 psi hydrogenwithout heating. Within 30 minutes, the temperature had risen to 55° C.and after 6 hours the temperature had returned to room temperature.Fourier transform infra-red showed that essentially all of the butadieneunsaturation had been hydrogenated and that 70% of the isoprenevinylidene groups remained. Hydrogenation was stopped and catalystresidues were removed by citric acid washing followed by inverse alcoholflocculation to give the desired pentablock copolymer (c) as alight-colored solid mass with a reduced tendency to cold-flow.

The procedure of this example can also be followed in preparing triblockcopolymer (a) except that, instead of preparing an initial livingtriblock by sequential addition of isoprene, butadiene and, afterremoval of THF, an additional amount of butadiene, the initial amountsof isoprene and butadiene are added to the reactor concurrently to forma living random copolymer of isoprene and butadiene wherein thepolymerized butadiene comprises significant proportions of 1,4- and1,2-units. A substantial percentage of THF is then removed as describedand an additional amount of butadiene is added which forms a livingdiblock wherein the second block is composed of polybutadiene containingat least about 80% of 1,4-units. This living diblock is then coupled asdescribed to form a precursor triblock copolymer containing end blocksof a random isoprene/butadiene copolymer wherein the polymerizedbutadiene comprises substantial proportions of 1,2-units as well as1,4-units, and a central polybutadiene block containing a greatlydecreased number of 1,2-units. The precursor polymer is then selectivelyhydrogenated as described to form triblock copolymer (a).

In addition to excellent resistance to cold flow, the unvulcanizedpolymers of Examples 1 and 3 as well as the other unvulcanized polymersof this invention have excellent oxidative, thermal and pyrolyticstability. After vulcanization, the polymers of the invention also haveexcellent elasticity at elevated temperatures and a high degree ofresistance to solvents.

It will be apparent to those skilled in the art that the specificembodiments discussed above can be successfully repeated withingredients equivalent to those generically or specifically set forthabove and under variable process conditions.

From the foregoing specification, one skilled in the art can readilyascertain the essential features of this invention and without departingfrom the spirit and scope thereof can adapt it to various diverseapplications.

We claim:
 1. A selectively hydrogenated, essentially straight chainsolid elastomeric block copolymer wherein the terminal blocks are each arandom IB copolymer of at least one diene I, said diene I containing atleast five carbon atoms with at least one of each pair of double-bondedcarbon atoms in the polymerized diene I units being additionally bonedto two carbon atoms, and hydrogenated butadiene (B), and at least onemiddle or interior block is an essentially straight chain polyethylene(E polymer) resulting from the hydrogenation of a polybutadiene composedof at least 80% of 1,4-units, the hydrogenated butadiene units in saidrandom IB copolymer blocks being composed of not more than about 65% of1,4-units and at least about 35% of 1,2-units and said random IBcopolymer blocks containing no more than about 10% of polyethylenecrystallinity, and the number of unsaturated polymerized diene I unitsin said random IB polymer blocks being sufficient to vulcanize saidblock copolymer.
 2. The block copolymer of claim 1 which has beensubjected to a vulcanization treatment.
 3. The block copolymer of claim1 comprising an average of about 70 to 99 wt. % of random IB copolymerblocks, and about 1 to 30 wt. % of E polymer blocks, all based on thetotal weight of block copolymer, with the polymerized I units being anaverage of about 1 to 50 wt. % of each random IB copolymer block, andthe remainder being polymerized butadiene (B).
 4. The block copolymer ofclaim 1 composed of three blocks wherein the end blocks are each saidrandom IB copolymer and the central block is said E polymer.
 5. Thetriblock copolymer of claim 4 having the formula

    (I.sub.x B.sub.y)-(E.sub.z)-(I.sub.x B.sub.y)

wherein x is the number of polymerized I units in each random IBcopolymer block and has an average value of about 7 to 368 (one half themolecular total), y is the number of hydrogenated polymerized butadiene(B) units in each random IB copolymer block and has an average value inthe range of about 185 to 908 (one half the molecular total), and z isthe number of straight chain polymerized units in the central E blockand has a value of about 37 to 1111, said values being per 100,000 M.W.6. The block copolymer of claim 5 wherein I is isoprene.
 7. The blockcopolymer of claim 6 which has been subjected to a vulcanizationtreatment.
 8. A sulfonated polymer produced by a method comprisingsulfonating the block copolymer of claim 1, followed by neutralizationof the thus formed polymeric sulfonic acid with metal ions or amines. 9.A maleated polymer produced by a method comprising contacting the blockcopolymer of claim 1 with maleic anhydride.
 10. An essentially straightchain precursor block copolymer wherein the terminal blocks are each arandom IB copolymer of at least one diene I, said diene I containing atleast five carbons atoms with at least one of each pair of double-bondedcarbon atoms in the polymerized diene I units being additionally bondedto two carbon atoms, and butadiene wherein the polymerized butadieneunits are composed of not more than about 65% of 1,4-units and at leastabout 35% of 1,2-units, and at least one middle or interior block ispolybutadiene composed of at least about 80% of polymerized 1,4-units.11. A triblock copolymer as recited in claim
 10. 12. The triblockcopolymer of claim 11 wherein said diene I is isoprene.
 13. Ahalogenated polymer produced by a method comprising halogenating theblock copolymer of claim 1.